Conventionally it is considered indispensable in manufacturing a mold that, to obtain a good casting by controlling the flow of molten metal and by restraining any involvement of any impure substance and gas in the product, a passage for the molten metal called a gating system, which has nothing to do with the shape of a casting (see, for example, Non-Patent Publication 1), is provided. However, the gating system often has lowered the yield rate of casting. Moreover, it also requires removing the gating system after crashing the mold. Thus the gating system often worked disadvantageously to the productivity and the cost efficiency of casting.
Therefore, to improve the yield rate for casting, it is proposed to use a molding method wherein it is carried out by using a lower mold, which is a main mold formed by various kinds of molding methods, and which has no gating system, but only a cavity required for casting, and an upper mold, which is a main mold formed by various kinds of molding methods, and has no cavity for a gating system, but which has a protruding portion capable of forming a cavity for casting. In this casting method it is proposed that, after the molten metal required to produce only the casting is poured into the cavity of the lower mold, the protruding portion of the upper mold be advanced into the cavity filled with the molten metal so as to form the cavity required to produce the casting, and that then the upper mold overlap the lower mold.
In the casting method according to the present invention, for the mold that makes unnecessary the work of eliminating, from castings, gating system, feeders etc., that are used in the method based on the gating system plan, a lower mold and a upper mold are disclosed. In this method the lower mold is a main mold formed by various kinds of mold-forming methods, and has no cavity for a gating system, but only a cavity for casting, and the upper mold is a main mold formed by various kinds of mold-forming methods, and has no cavity for a gating system, but has a protruding portion capable of forming a cavity for castings in combination with a cavity of the lower mold. Further also disclosed is adding a flow-off cavity, i.e., a cavity necessary for castings. By adding this flow-off cavity it becomes possible to obtain some tolerance in the amount of such molten metal that is required to produce the casting.
[Non-Patent Publication 1]
Nihon Chuzou Kogakukai (Japan Foundry Engineering Society),
Illustrated Foundry Dictionary, 1st Ed.,
published by Nikkan Kogyo Sinbunsha, Japan, Nov. 30, 1995, page 212, gating system, and
[Patent Publication 1] Patent Application Publication Gazette No. JP2005-52871